An Analytical Inflation Model with Born－Infeld Type Scalar Field

We propose an analytical inflation model driven by a scalar field with Born-Infeld-type Lagrangian and compute its power spectrum. The constraints on the parameters of the potential by the recent Wilkinson-microwave anisotropy-probe data are derived.     

Scalar Field Model of Dark Energy In the Double Complex Symmetric Gravitational Theory

The scalar field model of dark energy is established in the double complex symmetric gravitational theory. The universe we live in is taken as the real part of double complex space M^4C（J）. The two cases of scalar field （ordinary and phantom scalar field） are discussed in a unified way. Not only can the double Friedmann equations be obtained, but also the equation of state for dark energy, potential V（φ） and scalar field φ can be expressed. Hence, a new method is proposed to study dark energy and the evolution of the universe.     

Improved Quark Mass Density-Dependent Model with Non-Linear Scalar Interaction

We present an improved quark mass density-dependent model which includes the quark and non-linear scalar field coupling. The wavefunction of quark is given. The rms charge radius, the magnetic moment, and the ratio between the axial-vector and the vector β-decay coupling constants of the nucleon are calculated. We find that the results given the present model are in agreement with experiments.     

The Born–Infeld sphaleron

We study the SU(2) electroweak model in which the standard Yang–Mills coupling is supplemented by a Born–Infeld term. The deformation of the sphaleron and bisphaleron solutions due to the Born–Infeld term is investigated and new branches of solutions are exhibited. Especially, we find a new branch of solutions connecting the Born–Infeld sphaleron to the first solution of the Kerner–Gal'tsov series.     

General holographic superconductor models with Born–Infeld electrodynamics

A general class of holographic superconductor models in Schwarzschild AdS black hole with the Born–Infeld electrodynamics is investigated. It is found that the Born–Infeld coupling parameter affects the critical temperature, the order of phase transitions, the conductivity and the critical exponents near the second-order phase transition point. It is also noted that both the position of the conductivity coherence peak and the ratio of the gap frequency in conductivity to the critical temperature depend on the model parameters and the Born–Infeld coupling parameter.     

Can Inflation, Dark Matter and Dark Energy Be Described in Terms of a Single, Real Scalar Field?

In this article, our aim is to consider inflation, dark energy and dark matter in the framework of a real scalar field. To this end, we use the quintessence approach. We have tried a real scalar field with a specific self-interaction potential in a spacially flat universe. Numerical results indicate that this potential can drive the expansion of the universe in three distinct phases. The first phase behaves as an inflationary expansion. For this stage, setting the scalar field’s initial value to ϕ ₀≥1.94 leads to N 3 68\mathcal{N}\geq 68 favored by observation. After the inflationary phase, the scalar field starts an oscillatory behavior which averages to a =0\bar{w}=0 fluid. This stage can be taken as a cold dark matter (p≈0) epoch expected from works on the structure formation issue. Observations and cosmological models indicate that t _inf ≈10⁻³⁵ s and the matter dominated lasts for t _m ≈10¹⁷ s, hence (\fract_mt_inf)_obs ? 10⁵²(\frac{t_{m}}{t_{inf}})_{obs}\approx10^{52}. We have shown that the present model can satisfy such a constraint. Finally, the scalar field leaves the oscillatory behavior and once again enters a second inflationary stage which can be identified with the recent accelerated expansion of the universe. We have also compared our model with the ΛCDM model and have found a very good agreement between the equation of state parameter of both of models during the DM and DE era.     

Shock wave polarizations and optical metrics in the Born and the Born–Infeld electrodynamics

We analyze the behavior of shock waves in nonlinear theories of electrodynamics. For this, by use of generalized Hadamard step functions of increasing order, the electromagnetic potential is developed in a series expansion near the shock wave front. This brings about a corresponding expansion of the respective electromagnetic field equations which allows for deriving relations that determine the jump coefficients in the expansion series of the potential. We compute the components of a suitable gauge-normalized version of the jump coefficients given for a prescribed tetrad compatible with the shock front foliation. The solution of the first-order jump relations shows that, in contrast to linear Maxwell’s electrodynamics, in general the propagation of shock waves in nonlinear theories is governed by optical metrics and polarization conditions describing the propagation of two differently polarized waves (leading to a possible appearance of birefringence). In detail, shock waves are analyzed in the Born and Born–Infeld theories verifying that the Born–Infeld model exhibits no birefringence and the Born model does. The obtained results are compared to those ones found in literature. New results for the polarization of the two different waves are derived for Born-type electrodynamics.     

A self-gravitating Dirac–Born–Infeld global monopole

We generalize the field theory of the global monopole to the Dirac–Born–Infeld (DBI) field and investigate the gravitational property of a DBI global monopole in four-dimensional spherically symmetric spacetime. The coupled equations for the metric and the DBI scalar field are solved asymptotically and numerically. It is found that, just as for a canonical global monopole, the gravitational effect of the DBI global monopole is equivalent to that of a deficit solid angle in the metric plus a negative mass at the origin. However, compared with a canonical global monopole, for the same false vacuum and symmetry-breaking scale, a DBI global monopole has a relatively smaller core and a larger absolute value of effective mass. Thus, it can yield a larger deflect angle when the light is passing by. Especially, when the scale of the warp factor is small enough, the effective mass of a DBI global monopole does not depend apparently on the value of the false vacuum, which is qualitatively different from that of a canonical global monopole.     

Geonic black holes and remnants in Eddington-inspired Born–Infeld gravity

We show that electrically charged solutions within the Eddington-inspired Born–Infeld theory of gravity replace the central singularity by a wormhole supported by the electric field. As a result, the total energy associated with the electric field is finite and similar to that found in the Born–Infeld electromagnetic theory. When a certain charge-to-mass ratio is satisfied, in the lowest part of the mass and charge spectrum the event horizon disappears, yielding stable remnants. We argue that quantum effects in the matter sector can lower the mass of these remnants from the Planck scale down to the TeV scale.     

A Parametric Dynamic Model of Dark Energy

The double complex symmetric gravitational theory is extended to the parametric symmetric gravitational theory by introducing a parameter β. Hence parametric Friedmann-Robertson-Walker equations are obtained and some characters of dark energy in corresponding spaces are discussed by taking different values of β. In our method some previous results can be included as the special case of our results. It is worth noting that some characters of dark energy can be more intuitively described in our model. By analysis, we can predict that the fate of universe would be a Big Rip in the future, and also find that the state parameters for the two different constraint conditions wФ are consistent with the present cosmological observations.     

Higher-dimensional black holes with Dirac–Born–Infeld (DBI) global defects

It is well-known that the exact solution of non-linear \(\sigma \) model coupled to gravity can be perceived as an exterior gravitational field of a global monopole. Here we study Einstein’s equations coupled to a non-linear \(\sigma \) model with Dirac–Born–Infeld (DBI) kinetic term in D dimensions. The solution describes a metric around a DBI global defects. When the core is smaller than its Schwarzschild radius it can be interpreted as a black hole having DBI scalar hair with deficit conical angle. The solutions exist for all D, but they can be expressed as polynomial functions in r only when D is even. We give conditions for the mass M and the scalar charge \(\eta \) in the extremal case. We also investigate the thermodynamic properties of the black holes in canonical ensemble. The monopole alter the stability differently in each dimensions. As the charge increases the black hole radiates more, in contrast to its counterpart with ordinary global defects where the Hawking temperature is minimum for critical \(\eta \). This behavior can also be observed for variation of DBI coupling, \(\beta \). As it gets stronger (\(\beta \ll 1\)) the temperature increases. By studying the heat capacity we can infer that there is no phase transition in asymptotically-flat spacetime. The AdS black holes, on the other hand, undergo a first-ordered phase transition in the Hawking–Page type. The increase of the DBI coupling renders the phase transition happen for larger radius.     

Holographic superconductors in the Born–Infeld electrodynamics

We study the effects of the Born–Infeld electrodynamics on the holographic superconductors in the background of a Schwarzschild–AdS black hole spacetime. We find that the presence of Born–Infeld scale parameter decreases the critical temperature and the ratio of the gap frequency in conductivity to the critical temperature for the condensates. Our results mean that it is harder for the scalar condensation to form in the Born–Infeld electrodynamics.     

Viscous Dark Energy Models with Variable G and Λ

We consider a cosmological model with bulk viscosity η and variable cosmological A ∝p^-α, alpha = const and gravitational G constants. The model exhibits many interesting cosmological features. Inflation proceeds du to the presence of bulk viscosity and dark energy without requiring the equation of state p =-p. During the inflationary era the energy density p does not remain constant, as in the de-Sitter type. Moreover, the cosmological and gravitational constants increase exponentially with time, whereas the energy density and viscosity decrease exponentially with time. The rate of mass creation during inflation is found to be very huge suggesting that all matter in the universe is created during inflation.     

Wormhole solutions in Gauss–Bonnet–Born–Infeld gravity

A new class of solutions which yields an (n + 1)-dimensional spacetime with a longitudinal nonlinear magnetic field is introduced. These spacetimes have no curvature singularity and no horizon, and the magnetic field is non singular in the whole spacetime. They may be interpreted as traversable wormholes which could be supported by matter not violating the weak energy conditions. We generalize this class of solutions to the case of rotating solutions and show that the rotating wormhole solutions have a net electric charge which is proportional to the magnitude of the rotation parameter, while the static wormhole has no net electric charge. Finally, we use the counterterm method and compute the conserved quantities of these spacetimes.     

Friedmann Cosmology with Bulk Viscosity： A Concrete Model for Dark Energy

The universe content is considered as a non-perfect fluid with bulk viscosity and can be described by a general equation of state （endowed some deviation from the conventionally assumed cosmic perfect fluid model）. An explicitly bulk viscosity dark energy model is proposed to confront consistently with the current observational data sets by statistical analysis and is shown consistent with （not deviated away much from） the concordant A Cold Dark Matter （CDM） model by comparing the decelerating parameter. Also we compare our relatively simple viscosity dark energy model with a more complicated one by contrast with the concordant ACDM model and find our model improves for the viscosity dark energy model building. Finally we discuss the perspectives of dark energy probes for the coming years with observations.